1. Technical Field of the Invention
The present invention relates generally to the encryption of communications between a mobile station and a network, and more particularly, to a method and apparatus for encryption between a mobile switching center node and a packet mobile switching center node utilizing an encryption algorithm stored only on a single node.
2. Description of Related Art
In a mobile cellular communications system the information which is transmitted between the network and a mobile station (MS) must be protected from undesired interception. This is accomplished by encrypting transmissions sent over the air interface between the mobile station and the network. This is normally accomplished by using some type of encryption algorithm which is executed between the network and the mobile station. Voice communication encryptions are handled by a mobile switching center (MSC) node.
The continued development of wireless communications have added the ability for a mobile station to utilize both voice communications and packet-switched communications. Packet-switched communications are handled between a mobile station and a packet mobile switching center (PMSC) packet-switching node. By introducing packet-switched communications services within a communications system, the mobile station is connected to the PMSC through the air interface when transmitting packet data.
Since the algorithm for calculating the encryption key is secret and complex, it is not a preferred solution to implement the same algorithm on the PMSC node along with the algorithm on the MSC node. Furthermore, by implementing the algorithm on two separate nodes, synchronization problems may occur during hardware/software upgrades of the nodes. Thus, some method for enabling encryption between the mobile station and both MSC and PMSC nodes is desired.